Thin couplers and reflectors for sensing waveguides

ABSTRACT

An optical touch-sensitive device is able to determine the locations of multiple simultaneous touch events. The optical touch-sensitive device can include an optical waveguide, an emitter, and an emitter coupler. The emitter produces optical beams, and the emitter coupler is on a surface of the waveguide and is configured to direct at least some of the optical beams to propagate via total internal reflection (TIR) through the waveguide as coupled optical beams. Touches on the top surface of the waveguide disturb the coupled optical beams, and the touch-sensitive device determines touch events based on the disturbances.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of prior, co-pending U.S. ApplicationNo. 16/156,817, filed on Oct. 10, 2018, which claims priority to U.S.Provisional Patent Application No. 62/570,558, titled “Thin Couplers andReflectors for Sensing Waveguides,” filed on Oct. 10, 2017, both ofwhich are incorporated by reference herein in their entirety.

BACKGROUND 1. Field of Art

The present disclosure relates to optical couplers, and specifically, tooptical couplers in touch-sensitive devices.

2. Description of the Related Art

Touch-sensitive devices (e.g., touch-sensitive displays) for interactingwith computing devices are becoming more common. A number of differenttechnologies exist for implementing touch-sensitive devices. Examples ofthese techniques include, for example, resistive touch screens, surfaceacoustic wave touch screens, capacitive touch screens, and certain typesof optical touch screens.

However, many of these approaches currently suffer from drawbacks. Forexample, some technologies may function well for small sized displays,as used in many modem mobile phones, but do not scale well to largerscreen sizes as in displays used with laptop computers, desktopcomputers, interactive whiteboards, etc. For technologies that require aspecially processed surface or the use of special elements in thesurface, increasing the screen size by a linear factor of N means thatthe special processing must be scaled to handle the N² larger area ofthe screen or that N² times as many special elements are required. Thiscan result in unacceptably low yields or prohibitively high costs.

Another drawback for some technologies is their inability or difficultyin handling multitouch events. A multitouch event occurs when multipletouch events occur simultaneously. This can introduce ambiguities in theraw detected signals, which then must be resolved. If such ambiguitiesare not resolved in a speedy and computationally efficient manner it maymake implementation of the technology impractical or unviable. If tooslow, then the technology will not be able to deliver the touch samplingrate desired for the system. If too computationally intensive, then thiswill drive up the cost and power consumption of the technology.

One type of optical touchscreen involves coupling light from emittersinto a waveguide, however existing techniques can represent asignificant manufacturing cost. Thus, there is a need for improvedtouch-sensitive systems.

SUMMARY

Some embodiments relate to an optical touch-sensitive device with anoptical waveguide, an emitter, and an emitter coupler. The opticalwaveguide extends over a surface of the device and has a top surface anda bottom surface. The emitter is optically coupled to the waveguide andconfigured to produce optical beams. The emitter coupler is on a surfaceof the waveguide and is configured to direct at least some of theoptical beams to propagate via total internal reflection (TIR) throughthe waveguide as coupled optical beams. Touches on the top surface ofthe waveguide disturb the coupled optical beams, and the touch-sensitivedevice determines touch events based on the disturbances. In someembodiments, the optical touch-sensitive device includes a detectoroptically coupled to the waveguide and a detector coupler. The detectorcoupler is on a surface of the waveguide and is configured to redirectat least some of the coupled optical beams out of the waveguide towardsthe detector.

Some embodiments relate to an optical touch-sensitive device with anoptical waveguide, one or more emitters, and an optical reflector. Theoptical waveguide has a surface, an opposing surface, and a sidesurface. The one or more emitters emit optical beams, the emittedoptical beams propagate via total internal reflection (TIR) in thewaveguide. Touches on the surface of the waveguide disturb the opticalbeams, and the touch-sensitive device determines touch events based onthe disturbances. The optical beams propagate at elevation anglesrelative to the plane of the surface of the waveguide. The opticalreflector is on a surface of the waveguide. The optical reflectorreflects optical beams propagating in the waveguide, wherein incidentoptical beams propagate through the waveguide at an initial elevationangle and reflected optical beams propagate through the waveguide at amodified elevation angle. The optical reflector includes a plurality ofreflective structures, a first one of the reflective structurescomprising a first surface and a second surface. The first surface isoriented to reflect optical beams incident at the initial elevationangle at the modified elevation angle as reflected optical beams. Thesecond surface is oriented to reflect a portion of the reflected opticalbeams at an intermediate elevation angle towards a second one of thereflecting structures. In some embodiments, the intermediate elevationangle is substantially equal to the negative of the initial elevationangle. In some embodiments, the beams propagating at the intermediateelevation angle towards the second reflecting structure redirect off ofa first surface of the second reflecting structure at the modifiedelevation angle. Additionally or alternatively, planar reflectors may beused to redirect beams. In some embodiments, the modified elevationangle is substantially equal to the initial elevation angle.

Some embodiments relate to an optical touch-sensitive device with anoptical waveguide, an emitter array, a detector array, an emittercoupler, a detector coupler, and one or more reflectors. The opticalwaveguide extends over a surface of the device, the waveguide having anactive area and a periphery. The emitter array is coupled to thewaveguide and is configured to produce concentrated optical beams. Thedetector array is coupled to the waveguide and is configured to receiveconcentrated optical beams. The emitter coupler is on the periphery ofthe waveguide. The emitter coupler includes optical structuresconfigured to distribute the concentrated optical beams from the emitterarray across the active area of the waveguide according to apredetermined pattern. Touches on the active area disturb the opticalbeams, and the touch-sensitive device determines touch events based onthe disturbances. The detector coupler is on the periphery of thewaveguide. The detector coupler includes optical structures configuredto receive at least some optical beams and concentrate the receivedoptical beams towards the detector array. The one or more reflectors areon the periphery. The reflectors include optical structures configuredto reflect optical beams across the active area and towards the detectorcoupler.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the present invention will now be described, by way ofexample, with reference to the accompanying drawings, in which:

FIG. 1 is a diagram of an optical touch-sensitive device, according toan embodiment.

FIG. 2 is a flow diagram for determining the locations of touch events,according to an embodiment.

FIGS. 3A-3B illustrate a frustrated TIR mechanism for a touchinteraction with an optical beam, according to an embodiment.

FIG. 3C illustrates a touch interaction with an optical beam enhancingtransmission, according to an embodiment.

FIGS. 4A-4C are top views of differently shaped beam footprints,according to some embodiments.

FIGS. 5A and 5B are top views illustrating active area coverage byemitters and detectors, according to some embodiments.

FIG. 6A is a top view of an optical touch-sensitive device with couplersand reflectors, according to an embodiment.

FIG. 6B is a perspective view of the optical-touch sensitive device withcouplers and reflectors, according to an embodiment.

FIGS. 7A and 7B are cross-sectional portions of a waveguide with anemitter coupler and reflector in a thin film on the top surface,according to some embodiments.

FIG. 7C is a top view of the coupler and reflector of FIGS. 7A and 7B,according to an embodiment.

FIGS. 8A and 8B illustrate cross-sectional views of a waveguide withreflectors on the bottom surface, according to some embodiments.

FIGS. 9A-9C illustrate reflectors on sides of the waveguide, accordingto some embodiments.

FIGS. 10A-10D illustrate various emitter coupler and reflectorarrangements, according to some embodiments.

FIG. 11 is a cross-sectional view of a detector coupler reflecting beamsto a detector array, according to an embodiment.

FIG. 12 is a cross-sectional view of beams reflected into and out of awaveguide by couplers, according to an embodiment.

FIG. 13 illustrates an arrangement of couplers and reflectors forcreating virtual emitters and detectors, according to an embodiment.

FIG. 14 illustrates a predetermined beam pattern to determine exampletouch event locations, according to an embodiment.

FIGS. 15-18 illustrate example reflector structures, according to someembodiments.

FIG. 19 illustrates a perspective view of beam paths reflected from acoupler structure, according to an embodiment.

FIG. 20 is a perspective view of an emitter array and couplerstructures, according to an embodiment.

The figures depict various embodiments of the present disclosure forpurposes of illustration only. One skilled in the art will readilyrecognize from the following discussion that alternative embodiments ofthe structures and methods illustrated herein may be employed withoutdeparting from the principles of the disclosure described herein.

DETAILED DESCRIPTION I. Introduction

-   -   A. Device Overview

FIG. 1 is a diagram of an optical touch-sensitive device 100, accordingto one embodiment. The optical touch-sensitive device 100 includes acontroller 110, emitter/detector drive circuits 120, and atouch-sensitive surface assembly 130. The surface assembly 130 includesan active area 131 over which touch events are to be detected. Forconvenience, the active area 131 may sometimes be referred to as theactive surface or surface, as the active area itself may be an entirelypassive structure such as an optical waveguide. The assembly 130 alsoincludes emitters and detectors arranged along the periphery of theactive area 131. In this example, there are J emitters labeled as Ea-EJand K detectors labeled as D1-DK. The device also includes a touch eventprocessor 140, which may be implemented as part of the controller 110 orseparately as shown in FIG. 1. A standardized API may be used tocommunicate with the touch event processor 140, for example between thetouch event processor 140 and controller 110, or between the touch eventprocessor 140 and other devices connected to the touch event processor.In other embodiments, emitters and detectors may be located around aportion of the periphery and reflectors can be used to obtain a desireddistribution of beams over the surface.

The emitter/detector drive circuits 120 serve as an interface betweenthe controller 110 and the emitters Ej and detectors Dk. The emittersproduce optical “beams” which are received by the detectors. Preferably,the light produced by one emitter is received by more than one detector,and each detector receives light from more than one emitter. Forconvenience, “beam” will refer to the light from one emitter to onedetector, even though it may be part of a large fan of light that goesto many detectors rather than a separate beam. The beam from emitter Ejto detector Dk will be referred to as beam jk. FIG. 1 expressly labelsbeams a1, a2, a3, e1, and eK as examples. Touches within the active area131 will disturb certain beams, thus changing what is received at thedetectors Dk. Data about these changes is communicated to the touchevent processor 140, which analyzes the data to determine thelocation(s) (and times) of touch events on surface 131.

-   -   B. Process Overview

FIG. 2 is a flow diagram for determining the locations of touch events,according to one embodiment. This process will be illustrated using thedevice of FIG. 1. The process 200 is roughly divided into two phases,which will be referred to as a physical phase 210 and a processing phase220. Conceptually, the dividing line between the two phases is a set oftransmission coefficients Tjk.

The transmission coefficient Tjk is the transmittance of the opticalbeam from emitter j to detector k, compared to what would have beentransmitted if there was no touch event interacting with the opticalbeam.

The use of this specific measure is purely an example. Other measurescan be used. In particular, since we are most interested in interruptedbeams, an inverse measure such as (1−Tjk) may be used since it isnormally zero. Other examples include measures of absorption,attenuation, reflection, or scattering. In addition, although FIG. 2 isexplained using Tjk as the dividing line between the physical phase 210and the processing phase 220, it is not required that Tjk be expresslycalculated. Nor is a clear division between the physical phase 210 andprocessing phase 220 required.

Returning to FIG. 2, the physical phase 210 is the process ofdetermining the Tjk from the physical setup. The processing phase 220determines the touch events from the Tjk. The model shown in FIG. 2 isconceptually useful because it somewhat separates the physical setup andunderlying physical mechanisms from the subsequent processing.

For example, the physical phase 210 produces transmission coefficientsTjk. Many different physical designs for the touch-sensitive surfaceassembly 130 are possible, and different design tradeoffs will beconsidered depending on the end application. For example, the emittersand detectors may be narrower or wider, narrower angle or wider angle,various wavelengths, various powers, coherent or not, etc. As anotherexample, different types of multiplexing may be used to allow beams frommultiple emitters to be received by each detector.

The interior of block 210 shows one possible implementation of process210. In this example, emitters transmit 212 beams to multiple detectors.Some of the beams travelling across the touch-sensitive surface aredisturbed by touch events. The detectors receive 214 the beams from theemitters in a multiplexed optical form. The received beams arede-multiplexed 216 to distinguish individual beams jk from each other.Transmission coefficients Tjk for each individual beam jk are thendetermined 218.

The processing phase 220 can also be implemented in many different ways.Candidate touch points, line imaging, location interpolation, touchevent templates, and multi-pass approaches are all examples oftechniques that may be used as part of the processing phase 220.

II. Physical Set-up

The touch-sensitive device 100 may be implemented in a number ofdifferent ways. The following are some examples of design variations.

-   -   A. Electronics

With respect to electronic aspects, note that FIG. 1 is exemplary andfunctional in nature. Functions from different boxes in FIG. 1 can beimplemented together in the same component.

-   -   B. Touch Interactions

Different mechanisms for a touch interaction with an optical beam can beused. One example is frustrated total internal reflection (TIR). Infrustrated TIR, an optical beam is confined to an optical waveguide bytotal internal reflection and the touch interaction disturbs the totalinternal reflection in some manner. FIGS. 3A-3B illustrate a frustratedTIR mechanism for a touch interaction with an optical beam.

The touch interactions can also be direct or indirect. In a directinteraction, the touching object 304 (e.g., a finger or stylus) is theobject that interacts with the optical beam 302. For example, a fingermay have a higher index of refraction than air, thus frustrating TIRwhen the finger comes into direct contact with a waveguide. In anindirect interaction, the touching object 304 interacts with anintermediate object, which interacts with the optical beam 302 (theoptical beam 302 travels within the optical waveguide at elevation angle306, as further described below). For example, the finger may cause ahigh index object to come into contact with the waveguide, or may causea change in the index of refraction of the waveguide or surroundingmaterials.

Note that some types of touch interactions can be used to measurecontact pressure or touch velocity, in addition to the presence oftouches. Also note that some touch mechanisms may enhance transmission,instead of or in addition to reducing transmission. FIG. 3C illustratesa touch interaction with an optical beam enhancing transmission. Forsimplicity, in the remainder of this description, the touch mechanismwill be assumed to be primarily of a blocking nature, meaning that abeam from an emitter to a detector will be partially or fully blocked byan intervening touch event. This is not required, but it is convenientto illustrate various concepts.

For convenience, the touch interaction mechanism may sometimes beclassified as either binary or analog. A binary interaction is one thatbasically has two possible responses as a function of the touch.Examples includes non-blocking and fully blocking, or non-blocking and10%+attenuation, or not frustrated and frustrated TIR. An analoginteraction is one that has a “grayscale” response to the touch:non-blocking passing through gradations of partially blocking toblocking.

-   -   C. Emitters, Detectors, and Couplers

Each emitter transmits light to a number of detectors. Usually, eachemitter outputs light to more than one detector simultaneously.Similarly, each detector receives light from a number of differentemitters. The optical beams may be visible, infrared, and/or ultraviolet(UV) light. The term “light” is meant to include all of thesewavelengths and terms such as “optical” are to be interpretedaccordingly.

Examples of the optical sources for the emitters include light-emittingdiodes (LEDs), vertical-cavity surface-emitting lasers (VCSELs), andlasers. IR sources can also be used. Modulation of the optical beams canbe external or internal. Examples of sensor elements for the detectorinclude charge coupled devices, photodiodes, photoresistors,phototransistors, and nonlinear all-optical detectors.

The emitters and detectors may also include optics and/or electronics inaddition to the main optical source or sensor element. For example,emitters and detectors may incorporate or be attached to lenses tospread and/or collimate emitted or incident light. Additionally, one ormore optical coupling assemblies (couplers) of varying design can beused to couple the emitters and detectors to the waveguide.

-   -   D. Optical Beam Paths

FIGS. 4A-4C are top or side views of differently shaped beam footprints.Another aspect of a touch-sensitive system is the shape and location ofthe optical beams and beam paths. In FIGS. 1-2, the optical beams areshown as lines. These lines should be interpreted as representative ofthe beams, but the beams themselves may be different shapes andfootprints. A point emitter and point detector produce a narrow “pencil”beam 410 with a line-like footprint. A point emitter and wide detector(or vice versa) produces a fan-shaped beam 420 with a triangularfootprint. A wide emitter and wide detector produces a “rectangular”beam 430 with a rectangular footprint of fairly constant width.Depending on the width of the footprint, the transmission coefficientTjk behaves as a binary or as an analog quantity. It is binary if thetransmission coefficient transitions fairly abruptly from one extremevalue to the other extreme value as a touch point passes through thebeam. For example, if the beam is very narrow, it will either be fullyblocked or fully unblocked. If the beam is wide, it may be partiallyblocked as the touch point passes through the beam, leading to a moreanalog behavior.

Beams may have footprints in both the lateral (horizontal) direction, aswell as in the vertical direction. The lateral footprint of a beam maybe the same or different from the horizontal footprint of a beam.

The direction and spread of the light emitted from the emitters andreceived by the detectors may vary in spread or angle from beamfootprints intended to cover the active area 131. To shape the beams toachieve the intended footprints, lenses, couplers, reflectors, or otheroptical structures may be attached to the emitters and detectors. Forexample, point emitters and detectors may be used in conjunction withlenses to spread beams in the horizontal or vertical directions.

FIGS. 5A-5B are top views illustrating active area 131 coverage byemitters and detectors. As above, the emitters and detectors arearranged along the periphery of the active area 131. All the emittersmay be arranged on two sides of the active area, for example twoadjacent perpendicular sides as illustrated in FIG. 5A. Similarly, allof detectors may be arranged on the other two sides of the active area.Alternatively, the emitters and detectors may be mixed or interleavedaccording to a pattern as illustrated in FIG. 5B. This pattern may beone emitter in between each detector, or another more complicatedarrangement.

In most implementations, each emitter and each detector will supportmultiple beam paths, although there may not be a beam from each emitterto every detector. The aggregate of the footprints from all beams fromone emitter will be referred to as that emitter's coverage area. Thecoverage areas for all emitters can be aggregated to obtain the overallcoverage for the system.

The footprints of individual beams can be described using differentquantities: spatial extent (i.e., width), angular extent (i.e., radiantangle for emitters, acceptance angle for detectors), and footprintshape. An individual beam path from one emitter to one detector can bedescribed by the emitter's width, the detector's width and/or the anglesand shape defining the beam path between the two. An emitter's coveragearea can be described by the emitter's width, the aggregate width of therelevant detectors and/or the angles and shape defining the aggregate ofthe beam paths from the emitter. Note that the individual footprints mayoverlap. The ratio of (the sum of an emitter's footprints)/(emitter'scover area) is one measure of the amount of overlap.

The emitters can provide a desired coverage of the active area 131.However, not all points within the active area 131 will be coveredequally. Some points may be traversed by many beam paths while otherpoints traversed by far fewer. The distribution of beam paths over theactive area 131 may be characterized by calculating how many beam pathstraverse different (x,y) points within the active area. The orientationof beam paths is another aspect of the distribution. An (x,y) point thatis derived from three beam paths that are all running roughly in thesame direction usually will be a weaker distribution than a point thatis traversed by three beam paths that all run at sixty degree angles toeach other.

The concepts described above for emitters also apply to detectors. Adetector's coverage area is the aggregate of all footprints for beamsreceived by the detector.

If the emitters and/or detectors are equally spaced along the sides ofthe active area 131, there may be large numbers of redundant beam paths.Thus, the emitters and/or detectors may not be evenly spaced apart. Thismay be referred to as dithering. Dithering can reduce the total numberof emitters and detectors while ensuring a desired coverage of theactive area 131.

Instead of arranging emitters and detectors along the entire peripheryof the active area 131, optical couplers and reflectors can allow theemitters and detectors to be reduced and condensed into one or moreemitter and detector arrays. Among other advantages, emitter anddetector arrays can decrease manufacturing cost and complexity. This isfurther described below.

III. Optical Couplers, Reflectors, and Related Hardware

-   -   A. General Description

As introduced above, the optical touch-sensitive device 100 includes anoptical waveguide that is optically coupled to the emitters anddetectors with one or more optical coupler assemblies (or couplers). Theoptical touch-sensitive device may also include one or more reflectors,printed circuit boards (PCBs), ambient light shields, IR transmissivelayers, air gaps and associated ambient light absorbing surfaces, ordisplay modules.

FIGS. 6A and 6B illustrate a touch-sensitive device 100 with an emitterarray 615 and detector array 640, according to an embodiment. Touchevents, detected using frustrated TIR, are received within the activearea 131 of the top surface of the waveguide 605. The surface assembly130 includes an emitter array 615, an emitter coupler 630, a detectorarray 640, a detector coupler 645, and reflectors 625 attached to thewaveguide 605. Instead of emitters and detectors positioned along theentire periphery of the active area 131, a single emitter array 615 anddetector array 640 can be used in combination with reflectors 625 andcoupler 630, 645. Specifically, reflectors 625 are arranged along thetop, left, and right sides of the active area 131. The remainingcomponents are positioned along the bottom side. However, the emitterarray 615, emitter coupler 630, detector array 640, detector coupler645, and reflector 625 positions can be arranged differently. Forexample, additional emitter/detector arrays and couplers can bepositioned along the periphery.

As described above, optical beams travel through the waveguide 605 usingTIR. That is, optical beams reflect off the top and bottom surfaces ofthe waveguide 605 at angles greater than a critical angle from thenormal of the top and bottom surfaces of the waveguide 605. The angle ofa beam relative to the plane of a surface on which it is incident (e.g.,the top or bottom surface of the waveguide) may be referred to as theelevation angle or propagation angle. The angle of a beam relative tothe normal of a surface on which it is incident may be referred to asthe zenith angle. The elevation angle is equal to ninety minus thezenith angle.

The waveguide 605 may be constructed of a material that is rigid orflexible. Furthermore, the waveguide 605 can include one or more layersof material. These layers may be of similar indices of refraction andbehave much like a single body of material, or they may have differentindices of refraction. In some situations, beams travel through all ofthe layers of the waveguide 605 and in other situations beams may onlytravel through a subset of the layers. This can be due to the indices ofrefraction of the waveguide layers, the elevation angle of the beams,and the wavelengths of the beams. In the embodiment shown in FIG. 6, thewaveguide 605 has a top surface that is substantially or exactlyparallel to its bottom surface. The top surface of the waveguide isoriented to receive touch input. Although the waveguides within thecurrent disclosure are rectangular planar waveguides it should beappreciated that any shape and type of waveguide can be used. Forexample, the surfaces of the waveguide may be curved.

The emitter coupler 630 (or couplers) redirect beams emitted from theemitter array 615 (or emitter arrays) to have elevation angles such thatthey propagate through the waveguide 605 via TIR. The reflectors 625 mayredirect beams that are coupled into the waveguide 605 such that opticalbeams sufficiently cover the active area 131 to provide the desiredtouch resolution and are ultimately redirected to the detector array640. Thus, touch events can be detected anywhere on the active area 131.Beams 1, 2, and 3 are illustrated to demonstrate example beam paths.Beams 1 and 2 intersect at the location of touch event 1 and can thus beused to detect that touch event as propagation of these beams to thedetector array 640 may be partially or completely prevented by the touchevent. Beam 3 illustrates that the reflectors 625 can be configured toreflect beams in any arbitrary direction.

The optical touch-sensitive device 100 can be configured to operate inconjunction with a display (or screen) module configured to displayimages, however the display module is not necessarily part of theoptical touch sensitive device 100. In some applications, the waveguidecan be placed in front of the display device and can extend past thelateral edge of the display module. In other applications, the waveguidecan be formed on the front of the display device.

In the embodiment shown in FIG. 6, the emitter array 615 is locatedbelow the waveguide (e.g., along the periphery of the active area 131)and produces optical beams that enter the waveguide through bottomsurface of the waveguide e.g., by the emitter coupler 630. The emitterarray 615 can be any arrangement of the one or more previously describedemitters. For example, the emitter array 615 includes a one ortwo-dimensional array of LEDs. The detector array 640 is also locatedbelow the waveguide (e.g., along the periphery of the active area 131)and receives optical beams redirected by the detector coupler 645. Thedetector array 640 can be any arrangement of the one or more previouslydescribed detectors. For example, the detector array 640 includes a oneor two-dimensional array of photodiodes. The detector array 640 can alsobe a camera or other image sensor, such as a complementarymetal-oxide-semiconductor (CMOS) detector.

-   -   B. Couplers and Reflectors

The couplers 630, 645 and reflectors 625 are optical structures that candirect, widen, slim, reflect, diffract, refract, disperse, amplify,reduce, combine, separate, polarize, or otherwise change properties ofthe beams as they propagate through the waveguide. Furthermore, eachcoupler or reflector can perform one or more of these effects. To dothis, the coupler and reflector structures can include metalizedfeatures, optical gratings, mirrors, prismatic structures, Fresnelstructures, corner reflectors, retroreflectors, and the like. In thedescription, the couplers and reflectors are described in terms of‘redirecting’ optical beams, however this is for purposes of simplicityof description to include any one or more of the beam property changesdescribed above as well as any other manipulation of optical beams notspecifically called out above.

The height of the couplers 630, 645 and reflectors 625 can be less thanor equal to 500 micrometers. In some embodiments, a coupler and/orreflector is a portion of a film and the thickness of the film is lessthan or equal to 500 micrometers (although the optical structure itselfmay be less than or equal to one hundred micrometers high). Any numberof couplers and reflectors may be positioned on the waveguide, and thecouplers and reflectors can be attached to or a part of any surface ofthe waveguide, such as the top, side, and/or bottom surfaces. Couplersand reflectors at the side surfaces of the waveguide may be coupledthrough air into the waveguide (see, e.g., FIG. 9B). The couplers andreflectors may be made with any number of materials including, forexample, metal, glass, and polymers.

The reflector 625 includes one or more optical structures that redirectoptical beams propagating in the waveguide 605 according to apredetermined pattern. The emitter coupler 630 includes one or moreoptical structures that redirect optical beams from the emitter array615 according to a predetermined pattern. Predetermined patternsgenerally include a pattern of beams paths that originate from theemitter array 615, provide desired coverage of the active area 131, andredirect towards the detector array 640. Thus, the emitter coupler 630may couple beams from the emitter array 615 into the waveguide. Similarto the emitter coupler 630, the detector coupler 645 includes one ormore optical structures that receive optical beams propagating throughthe waveguide according to the predetermined pattern and redirect thebeams to the detector array 640. This may include coupling beams fromthe waveguide into the detector array 640. Each emitter array 615 anddetector array 640 may have its own coupler, and, as illustrated in FIG.6B, the couplers or associated structures can physically connect thearrays to the waveguide. Among other advantages, an emitter coupler 630can redirect beams from a concentrated optical source, such as anemitter array 615, and distribute it widely over a large active area131. Similarly, a detector coupler 645 can redirect beams from a widerange of angles and concentrate them onto a concentrated detectorsource, such as a detector array 640.

Couplers and reflectors can also be designed to change beam footprints.Beams with smaller footprints are more sensitive to touch events whilebeams with wider footprints can cover a greater proportion of the activearea 131. Thus, by having different beam footprints, the touch device100 can have different touch sensitivity levels. Additionally, beamfootprints can be used for touch object differentiation. For example, aslim stylus tip may affect a wide beam footprint differently than afinger. Generally, the couplers and reflectors can be designed toprovide almost any desired distribution of beam directions andfootprints.

The couplers 630, 645 and reflectors 625 can be manufactured on thewaveguide, formed as a part of the waveguide (e.g., integrated into aportion of the waveguide), or be part of a separate component that isadded to the waveguide. For example, the couplers and reflectors can beformed by extrusion or injection molding. In one embodiment, thecouplers and reflectors are a portion of a flexible thin film 610attached to a surface of the waveguide 605, such as at or near theperiphery. The film 610 can include a protective layer and reduceinstallment complexity. In another embodiment, the structures of thecouplers and reflectors can be formed directly onto a surface of thewaveguide by methods such as hot embossing (e.g., for polymerwaveguides), UV embossing, casting (e.g., for glass or polymerwaveguides), etching (e.g., for glass or polymer waveguides), orablation (e.g., for glass or polymer waveguides). Alternatively, anotherlayer (e.g., a polymer which can be cast into the desired shape) can beattached directly onto the waveguide surface. Among other advantages,due to the manufacturing methods, embodiments of the couplers andreflectors can be low profile structures. For example, through hotembossing, the structures can have heights ranging from 1 millimeter(mm) to several hundred micrometers, and through hot or UV embossing thestructures can have heights ranging from a few micrometers to 100micrometers.

In the example of UV embossing, a film 610 with a liquid resin coatingis passed under a roller. The roller includes a negative of the intendedstructure on its surface. The liquid coating is shaped by the roller andUV energy (typically from a source under the film and passing throughit) triggers crosslinking polymerization within the liquid, curing itinto the intended shape. The result is a film with a cured resin layeron top which can have a sophisticated surface profile. Optional layers,such as adhesive coatings on the underside and metallization layers onthe structure side can be applied to the film to form the desiredstructure. The film can then be applied to the waveguide surface. Insome embodiments, the film is a part of the waveguide itself. Amongother advantages, the waveguide, couplers, and reflectors can beproduced from high-volume roll-to-roll manufacturing methods.

Couplers and reflectors are further described below. The opticalstructures of couplers and reflectors can be similar. Thus, a concept,design, arrangement, etc. for a given coupler or reflector may also beapplied to other couplers and reflectors. Furthermore, the couplers andreflectors can alter properties of the beams not specificallyillustrated in the figures. For example, couplers and reflectors maychange the beam width footprints and/or redirect optical beams into orout of the page. Couplers and reflectors may also shift the apparentendpoint of the beam or reflected beam. Descriptions of components in afigure may be applicable to similar components in other figures.Additionally, due to manufacturing imperfections, redirected opticalbeams may not be directed at the exact angles intended or expected.However, the angles of the redirected optical beams may be substantiallyequal to those described or shown (e.g., within 1 or 2 degrees).

-   -   C. Example Coupler and Reflector Arrangements

FIGS. 7A and 7B are cross-sectional portions of a waveguide 705 with anemitter coupler 730 and reflector 725 in a film 710 on the top surface,according to some embodiments. FIG. 7C is a top view of the emittercoupler 730 and reflector 725, according to an embodiment. The emittercoupler 730 and reflector 725 are a part of a film 710 attached to theperiphery of the top surface of the waveguide 705. The emitter 715 isbelow the waveguide and aligned with the emitter coupler 730. Thus,beams enter the waveguide through the bottom surface and are incident onthe emitter coupler 730. The emitter coupler 730 changes the angle ofthe beams so that the beams propagate via TIR. As seen in FIG. 7C (thetop view), the emitter coupler 730 distributes the beams in a radialpattern. The reflector 725 is placed between the emitter coupler 730 andthe edge of the waveguide 705 to redirect beams heading towards the edge(that would otherwise be lost) towards the active area 131 (e.g.,towards the detector array 740, another reflector 725, etc.).

The waveguide 705 includes several layers. In the embodiments shown, thelayers include a bottom glass layer 706 attached by adhesive 707 to atop polymer film 708. The glass layer 706 can also be a polymer, such asPolyethylene terephthalate (PET), Poly(methyl methacrylate) (PMMA),Polycarbonate (PC), or Polysiloxane (silicone), although any opticallytransmissive polymer may be suitable. Note that Polydimethylsiloxane(PDMS) can be suitable for making molds for microstructures. The glasslayer 706 can provide structural support to the other layers of thewaveguide. The emitter coupler 730 and reflector 725 are a part of afilm 710 attached to the top surface of the waveguide 705. The film 710can include a cured embossed polymer 720 in contact with the waveguide,a metallization layer 723 and a decorative layer 721 and a protectivetopcoat 722 on the polymer 720. The cured embossed polymer includes theemitter coupler 730 and reflector 725. The protective topcoat 722 canprotect the film 710 from being damaged and the decorative layer 721 canvisually cover the coupler 730 and reflector 725 from a user of thetouch device 100. The metal layer 723 can allow the cured embossedpolymer layer 720 to form reflectors 625 which are capable ofredirecting beams. For example, reflectors 625 can redirect beams atsmaller angles of incidence than might be possible with TIR (based onthe refractive index difference between the cured polymer and theadjoining material) alone. The total height of the film 710 and toplayers of the waveguide 705 (excluding the glass layer 706) be rangefrom 50 to 500 μm.

Alternative layers in the film 710 may be an air gap instead of themetallization layer 723 (where the air is trapped between the recessesin the embossed polymer 720 and the layer above the embossed polymer720). For example, the decorative layer 721 can be a tape with adhesiveon the underside which is applied to the embossed polymer 720, trappingair in the process. The air offers a low refractive index material offwhich beams in the embossed polymer 720 can be redirected.

The emitter coupler 730 and reflector 725 include an array of reflectivestructures to redirect the beams. These structures can be metalizede.g., the reflector 725 is an array of plane mirrors. As seen in FIG.7C, the reflected beams 735 propagate towards the active area 131 as ifthey were produced from a second emitter. Due to the physicalarrangement of the coupler 730 and reflector 725, additional emitterscan be virtualized and, thus, the coverage area of the active area 131can be increased without increasing the number of emitters or emitterarrays. Alternatively, if emitter coupler 730 redirects beams onlytowards the reflector 725, the reflected beams 735 can make the apparentemitter location to be along the reflector 725. In some embodiments, thereflected azimuth angles of the beams 735 do not match the incidentazimuth angles of the beams 735. For example, the reflector 725 hasnon-linear optical structures (e.g., a chevron pattern) that decreasethe reflected azimuth angles of the reflected beams 735. In anotherexample, beam 3 of FIG. 6B has a sharp reflected azimuth angle comparedto beams 1 and 2.

FIGS. 8A and 8B illustrate cross-sectional views of the waveguide 805with reflectors 825 on the bottom surface, according to someembodiments. In the example of FIGS. 8A and 8B, the waveguide includes aglass layer 806 attached to the top surface of the polymer film 808. Afilm 810 includes a reflector 825 in a cured polymer 820 attached to thebottom surface of the polymer film 808. In some embodiments, the heightof the glass layer 806 is four millimeters and the total height of theremaining layers (including the film layers 810) is one hundredmicrometers. Among other advantages, reflectors (and couplers) on thebottom surface of the waveguide 805 are protected (e.g., from touchevents) by the waveguide itself and, thus, a protective layer is notapplied. The reflectors 825 do not have to be in a film 810 and thelayers of the waveguide 805 and film 810 are not limited to thosedescribed in FIGS. 8A and 8B.

FIGS. 8A and 8B also illustrate reflectors 825 that change the elevationangle of beams (e.g., from thirty to fifteen degrees, which is a zenithangle change from sixty to seventy-five degrees). Before reflection, theoptical beams travel through the waveguide 805 via TIR at an initialelevation angle. After redirection, the beams travel at a smallerelevation angle. Among other advantages, changing the elevation angle ofbeams can change the sensitivity of the beams to touch events. This isbecause the zenith angle can be larger than the critical angle for thewaveguide material and a touch material. Also, due to the angle change,redirected optical beams may only travel through a subset of the layersof the waveguide. In FIG. 8B, the redirected optical beams areredirected by the adhesive 807 so that the beams travel via TIR in thepolymer film 808. As a result, the redirected optical beams may notpropagate through the glass layer 806 and are therefore not affected bytouches. For example, if n=1.41 (a typical value for a siliconeadhesive) for the adhesive 807 and n=1.56 (a typical value for apolycarbonate film) for the polymer film 808, beams with zenith anglesgreater than about 65 degrees will travel via TIR through the polymerfilm 808. For reference, example indices of refraction for the otherlayers include n=1.51 for the glass layer 806 and n=1.49 for the curedpolymer 820.

In FIG. 8A, the redirected beams continue to propagate through alllayers of the waveguide 805. However, due to the smaller elevation angleand the index of refraction of touch objects, the beams may be lesssensitive or insensitive to touch events. For example, if the glasswaveguide layer 806 is a PET film or sheet with n=1.64 and beams have anelevation angle of nineteen degrees, touch objects with n<1.55 will notaffect the beams (typical fingers have n values from 1.45 to 1.55). Inanother example, if n=1.51 for the glass layer 806, beams with anelevation angle of fifteen degrees will not be affected by touch objectswith n≤1.458. For reference, example indices of refraction for the otherlayers include n=1.49 for the adhesive 807, n=1.56 for the polymer film808, and n=1.49 for the cured polymer 820. In other embodiments, thevarious components may have different refractive indices.

In some embodiments, elevation angles can be used to distinguish touchtypes. For example, a group of beams are propagating at a firstelevation angle (e.g., thirty degrees) and another group of beams arepropagating at a second elevation angle (e.g., fifteen degrees). Thus,depending on the materials of the waveguide, finger touches may affectthe beams with the first elevation angle and styli with material tips(e.g., with a high index of refraction) may affect one or both sets ofbeams. In these embodiments, reflectors may retain the incidentelevation angles of beams instead of changing them.

Embodiments are not limited by those illustrated in FIGS. 8A and 8B. Forexample, the reflectors 825 may change the elevation angle from aninitial elevation angle to a larger elevation angle, rendering the beamssensitive or more sensitive to touch events after redirection.

FIGS. 9A-9B illustrate reflectors 925 on sides of the waveguide 905,according to some embodiments. The example waveguides 905 shown includea single layer, however additional layers may be present. In FIG. 9A,the reflector 925 is vertical and directly attached to the side of thewaveguide 905. Thus, redirected beams have the same or similar elevationangles as the incident beams. FIG. 9B is similar to FIG. 9A, except thatan air gap 904 is between the reflector 925 and waveguide. Among otheradvantages, this can avoid a difficult manufacturing step of attachingthe reflector to a narrow edge of the waveguide. For example, thereflector can be part of a waveguide housing. The air gap 904 can beincreased or decreased to alter the beams as desired. The air gap 904 ispreferably small to minimize beam lost above and below the reflector925. The height of reflector 925 can be larger than the waveguide 905thickness to simplify alignment of the waveguide 905 and reflector 925.In FIG. 9C, the reflector 925 is directly attached to the waveguide andplaced at an angle (e.g., 7.5 degrees) relative to the normal of the topsurface. Thus, the elevation angles of the redirected beams are changedrelative to the incident beams (e.g., from thirty to fifteen degrees).Note that the angles shown in FIG. 9C are zenith angles. In theseexamples, the reflectors 925 can be simple mirrors or a more complicatedoptical structure (e.g., if other optical effects are desired). In someembodiments, side reflectors 925 are used in conjunction with reflectorson other surfaces of the waveguide 905.

FIGS. 10A-10D illustrate various emitter coupler 1030 and reflector 1025arrangements, according to some embodiments. FIGS. 10A and 10B eachillustrate an emitter coupler 1030 and reflector 1025 on the bottomsurface, FIG. 10C illustrates an emitter coupler 1030 on the bottomsurface and a reflector 1025 on the top surface, and FIG. 10Dillustrates an emitter coupler 1030 as a part of the top surface of thewaveguide 1005. Emitter couplers 1030 on the bottom surface can includetransparent materials and may increase the proportion of optical energycoupled into the waveguide 1005. Emitter couplers 1030 on the bottomsurface may couple beams into the waveguide 1005 via diffractive orrefractive effects (e.g., the emitter coupler 1030 is a diffractiongrating or changes the angle of incident beams via refraction such thatthe elevation angle is sufficient for the beams to propagate via TIR).

In FIGS. 10A-10C, each emitter coupler 1030 couples optical beams intothe waveguide. The optical beams then propagate via TIR through thewaveguide due to the elevation angle imparted by the coupler 1030.Furthermore, each reflector 1025 decreases the elevation angle of thebeams coupled by the emitter coupler 1030, for example, to obtain adesired elevation angle or to decrease the elevation angle to one thatis sufficient for TIR to occur. In FIG. 10A, the emitter 1015 emitsbeams substantially perpendicular (e.g., within one or two degrees) tothe bottom surface of the waveguide, while in FIGS. 10B-10D, the emitter1015 is tilted at an angle relative to the bottom surface of thewaveguide. Arrangements with tilted emitters 1015 may have an increasedcoupling efficiency compared to arrangements without tilted emitters1015.

The reflector 1025 and emitter coupler 1030 of FIG. 10A are thin filmsattached to the bottom surface. In FIG. 10D, the emitter coupler 1030 isa part of the waveguide 1005 itself. This may be formed by embossing orcuring the coupler pattern directly onto the waveguide 1005 (e.g., thewaveguide is a polymer sheet). In some embodiments, the emitter coupler1030 of FIG. 10D is less than or equal to one millimeter (this may beintegrated into portion of a waveguide that is several millimetersthick). The reflectors 1025 of FIGS. 10B-10C and the emitter coupler1030 of FIG. 10D include prismatic structures. The prismatic structurescan include repeated inclined surfaces. Compared to other reflector andcoupler structures, prismatic structures can be more susceptible to beamlosses 1000 and outside beam intrusion 1001. However, prismaticstructures may be advantageous because they do not need to bemetallized, and thus can be easier to manufacture, and can be lesssensitive to being damaged (e.g., from impact or strong touch events).Thus, prismatic structures can be placed on the top surface without aprotective film.

FIG. 11 is a cross-sectional view of a detector coupler 1145 redirectingbeams to a detector or detector array 1140, according to an embodiment.Beams travel via TIR in the waveguide 1105 from the active area 131 andare incident on the detector coupler 1145. The detector coupler 1145redirects beams towards the detector array 1140. The redirected beamstravel through the bottom surface of the waveguide 1105 and are incidenton the detector array 1140. The waveguide 1105 can include additionallayers. Although not illustrated, other optical effects can be performedby the detector coupler 1145. For example, the detector coupler 1145 canredirect optical beams to an appropriate detector in the detector array1140 even if the beams are received at various elevation angles anddirections. Different detector couplers 1145 may be designed for varioustouch device arrangements and predetermined patterns.

FIG. 12 is a cross-sectional view of beams redirected into and out of awaveguide 1205 by couplers 1230, 1245, according to an embodiment. Thewaveguide 1205 includes a first layer 1201 on top of a second layer1202. The waveguide 1205 also includes tactile features 1200 on theactive area 131. The tactile features 1200 can provide a tactileexperience and reduce glare for a user interacting with thetouch-sensitive device 100. A film 1210 is attached to the periphery ofthe top surface of the first layer 1201 and includes an emitter coupler1230 and a detector coupler 1245. An emitter or emitter array 1215 isbelow the waveguide 1205 and is aligned with the emitter coupler 1230.Similarly, a detector or detector array 1240 is below the waveguide 1205and is aligned with the detector coupler 1245. Thus, beams from theemitter array are coupled into the waveguide, propagate via TIR throughthe first layer 1201, are coupled out of the waveguide, and are receivedby the detector array 1240.

In the example of FIG. 12, the beams do not travel through the secondlayer 1202 via TIR. As shown, the beams only travel through the secondlayer 1202 when being coupled into or out of the waveguide 1205. In somesituations, this may be advantageous. For example, the second layer 1202may be a cover lens for a display screen that does not initially providetouch detection, and the first layer 1201 (and other components) areadded to provide touch detection. In another example, the second layer1202 may be a material through which the beams cannot propagateefficiently via TIR (e.g., infrared wavelengths may not propagatethrough certain glass types). In some embodiments, the second layer 1202is 0.7 mm thick glass, the first layer 1201 is a 0.25 mm thick film, thetactile features 1205 are 20 μm thick, and the film 1210 includes a 25μm thick black lacquer over 27 μm thick couplers 630, 645. The blacklacquer layer may protect the couplers 630, 645 from damage during use.Furthermore, the couplers 630, 645 can be less than or equal to twomillimeters wide (e.g., 1.6 mm). Similar to FIG. 11, optical effects notillustrated may be performed by the detector couplers. For example, theoptical beams may propagate at a predetermined pattern with variouselevation angles, for instance, due to the emitter coupler 1230.Furthermore, other optical structures, such as reflectors may be presenton the waveguide 1205.

-   -   D. Multiple Emitters and Detectors

In some embodiments, it is advantageous to include multiple emitter anddetector arrays arranged along one or more sides of the active areas.These embodiments are further described below.

FIG. 13 illustrates an arrangement of couplers 1330, 1345 and reflectors1325 that can create virtual emitters and detectors, according to anembodiment. Emitter couplers 1330 and detector couplers 1345 arepositioned along the bottom side of the active area 131 and reflectors1325 are positioned along the top side. The emitter couplers 1330 canalso be emitters and the detector couplers 1345 can also be detectors.As illustrated, optical beams are directed from a central emittercoupler 1330 towards the reflectors 1325 along the top side. Thereflectors 1325 redirect the incident beams back towards the detectorcouplers 1345 along the bottom side. In some embodiments, differentand/or other components than those shown in FIG. 13 may be included. Forexample, additional reflectors or emitter/detector arrays may bearranged on the sides of the active area 131.

In some embodiments, the reflectors 1325 can appear as virtualdetectors. For example, the incident beams may be sensitive to touchevents and the reflectors 1325 change the elevation angle of the beamssuch that the redirected beams are insensitive to touch events. Thus,the detector couplers 1345 operate as if they are at the location of thereflectors 1325 because only the beam paths from the coupler 1330 to thereflectors 1325 are touch sensitive. In this way, the reflectors 1325are virtual detectors. Similarly, the reflectors 1325 can appear asvirtual emitters. For example, the incident beams may be insensitive totouch events and the reflectors 1325 change the beams such that theredirected beams are sensitive to touch events. Thus, the emittercouplers 1340 operate as if they are at the location of the reflectors1325 because only the beam paths from the reflectors 1325 to thedetector couplers 1345 are touch sensitive. Furthermore, combinations ofvirtual emitters and detectors can be used. For example, thepredetermined pattern of the emitter coupler 1330 includes touchsensitive and insensitive beams and the reflectors (or portions ofreflectors) are designed to redirect touch sensitive beams as touchinsensitive beams and redirect touch insensitive beams as touchsensitive beams. In another example, one or more emitter couplers 1330emit touch sensitive beams and one or more different emitter couplers1330 emit touch insensitive beams. Among other advantages, virtualemitters and detectors decreases manufacturing cost and complexitybecause, emitters and detectors are not installed along the entireperiphery of the active area 131. Also, using thin reflectors describedin this disclosure, the physical bulk of the reflectors is typicallysmaller than that of emitters and detectors along the periphery.

In the embodiment illustrated in FIG. 13, the reflectors 1325 aredithered (unequally spaced) along the top side. Dithering, can optimizethe distribution of beam paths in the active area 131 and can increasethe coverage area of the active area 131 without increasing the numberof emitters. Without couplers and reflectors, emitters and detectors maybe dithered on a PCB, which can be costly and difficult to manufacture,especially for touch devices with large active areas 131. Thus,dithering by couplers and reflectors, can decrease manufacturingcomplexity by allowing emitters and detectors to be manufactured on PCBswithout dithering.

FIG. 14 illustrates a predetermined beam pattern to determine exampletouch event locations, according to an embodiment. Emitters 1 and 2 anddetectors 1, 2, and 3 are arranged along the bottom side of the activearea 131 and reflectors 1425 are arranged along the top, left, and rightsides. Emitter 1 emits beams 1 and 2, detector 1 receives beam 1, anddetector 2 receives beam 2. Emitter 2 emits beam 3 (dashed line) anddetector 3 receives beam 3. Beams 1 and 2 can each be affected by atouch event at locations T1 or T2. Thus, determining whether a touchevent occurs at location T1 or T2 based solely on beams 1 and 2 can bedifficult or impossible. However, since beam 3 passes through locationT2 and does not pass through location T1, the location of the touchevent can be disambiguated as either being at location T1 or T2 bymeasuring beams 1, 2, and 3. Furthermore, by considering additionalbeams, simultaneous multiple touch events can be identified anddisambiguated from single touches.

-   -   E. Example Reflectors

FIGS. 15-18 illustrate examples reflector structures, according to someembodiments. The reflectors may be a linear or planar array of opticalstructures. The reflectors can be extended along a side (or portion of aside) of an active area e.g., similar to the reflector 725 of FIG. 7C.Furthermore, each of the reflectors include reflective structures thatcan be metal or include metalized features.

FIGS. 15 illustrates a cross-sectional view of a reflector 1525,according to a first embodiment. The reflector 1525 includes atriangular structure on the bottom surface of the waveguide. Thetriangular structure includes a reflective surface (e.g., a metalizedsurface) that redirects incident beams away from the reflector 1525. Thereflective surface of the structure is tilted at an angle relative tothe normal of the top surface of the waveguide. Thus, the redirectedoptical beams have a different elevation angle than the incident opticalbeams. In the example of FIG. 15, the elevation angles of the redirectedbeams are larger than those of the incident beams.

FIG. 16 is a cross-sectional view of a reflector 1625 according to asecond embodiment. The reflector 1625 includes a set of repeatinginclined reflecting surfaces (e.g., surfaces S1-S4). The reflectingsurfaces can be perpendicular to each other. The reflector 1625 isdesigned to retain the zenith angles of incident beams with sixty degreezenith angles. Although each set of repeating surfaces in FIG. 16 areidentical, each set of repeating surfaces can be different (e.g., eachset of repeating surfaces can be designed to retain other zenithangles). Example beam A with a zenith angle of sixty degrees is incidenton the reflector 1625. Beam A is redirected by S2 into a horizontal pathtowards S1. S2 is tilted by fifteen degrees with respect to a horizontalline (e.g., a line parallel to the waveguide) and is perpendicular toS1. Beam A is then redirected by S1 away from the reflector 1625 with azenith angle of sixty degrees. Thus, the initial zenith angle of beam Ais preserved. Since the initial and redirected elevation angles are thesame, beam A can strike any surface of the reflector 1625 and retain itsinitial zenith angle of sixty degrees. Although a plane mirror with anormal at sixty degrees can achieve a similar result for beam A (e.g.,similar to the reflector in FIG. 9C or FIG. 15), the plane mirror willbe less efficient for beams with zenith angles other than sixty degrees.Beams with various zenith angles, for example ranging from sixty tosixty-five degrees, may be propagating in the waveguide. Thus, a planemirror with a normal at sixty degrees will redirect an incident beamwith a zenith angle of sixty-five degrees at a zenith angle offifty-five degrees. As a result, the reflector 1625 can have a higherefficiency for beams with varying zenith angles. For example, beam Bwith a sixty-five degree zenith angle strikes S4 and S3 and isredirected away from the reflector with a retained sixty-five degreezenith angle.

FIG. 17 is a cross-sectional view of a reflector 1725 according to athird embodiment. The reflector 1725 includes alternating reflectingsurfaces (e.g., surfaces S1/S3 and S2/S4). The alternating surfaces form97.5 degrees angles with each other. The surfaces may be metalized toredirect the beams. The reflector 1725 is designed to increase thezenith angles of incident beams (e.g., from sixty to seventy-fivedegrees). For example, beam A is incident on S1 with a zenith angle ofsixty degrees. Upon redirection from S1, beam A propagates with a zenithangle of seventy-five degrees. However, if beams strike an alternatingsurface (e.g., S2 or S4), the redirected zenith angle is notseventy-five degrees. For example, beam B strikes S4 with a sixty degreezenith angle, redirects towards S3, and is redirected away from thereflector 1725 with a zenith angle of forty-five degrees. This canresult in beam loss. The proportion of beams incident on S1/S3 versesS2/S4 can be about 50%. Thus, significant portions of beams may not beredirected at zenith angles of seventy-five degrees.

FIG. 18 illustrates a cross-sectional view of a reflector 1825,according to a fourth embodiment. Due to the arrangement of itssurfaces, reflector 1825 can have a higher efficiency than reflector1725. Similar to the design in FIG. 17, the reflector 1825 can increasethe zenith angle of incident beams (e.g., from sixty to seventy-fivedegrees). The reflector 1825 includes a set of repeating surfaces (e.g.,surfaces S1-S3) that form an array of ridge structures along thereflector 1825. Although each set of repeating surfaces in FIG. 18 areidentical, each set of repeating surfaces can be different (e.g., eachset is oriented to redirect optical beams at different angles). Thereflector 1825 may be made of metal or the surfaces may be metalized toredirect the beams. Other suitable approaches to making the surfacesreflective may also be used. The height of the reflector 1825 can be assmall as a few micrometers.

The front reflecting surface (or “first reflecting surface”) of eachridge is orientated at an angle that redirects incident beams with anincreased zenith angle. For example, beam A is incident on S1 with azenith angle of sixty degrees. Upon redirection, beam A propagates awayfrom the reflector 1825 with a zenith angle of seventy-five degrees. Insome situations, instead of exiting the reflector 1825, a redirectedbeam will strike the opposing surface (or “second reflecting surface”).For example, beam B strikes S3 after redirecting from S1. The opposingsurface is tilted such that the beam can be redirected in the originaldirection and with a launch angle equal or substantially equal to theoriginal zenith angle (but with opposite sign). The resulting beam cantherefore be redirected off the bottom surface of the waveguide 1805(e.g., via TIR) and be directed towards another ridge of the reflector1825 where it can either be returned at the increased zenith angle oragain redirected further into the array of ridge structures. As aresult, the reflector 1725 can have a higher efficiency than reflector1825 due to the opposing surfaces redirecting beams back toward thewaveguide with the original zenith angle (or substantially the originalzenith angle).

In some embodiments, the combined thickness of the waveguide 1805 andreflector 1825 is chosen so that the overall number of reflections isreduced. However, in other embodiments the efficiency of the reflector1825 can still be higher than alternative designs, such as the one inFIG. 17.

-   -   F. Examples of Coupler Structures

FIG. 19 illustrates a perspective view of beam paths redirected from acoupler structure 1930, according to an embodiment. Beams are emittedfrom an emitter 1915, such as a VCSEL. The coupler structure 1930 is aprism and may be a part of an emitter coupler. The emitter 1915 may be apart of an emitter array. In the embodiment shown, the emitter 1915 isbelow the bottom surface of the waveguide 1905 and the coupler structure1930 is above the top surface of the waveguide 1905. Optical beamspropagate from the emitter 1915 towards the coupler structure 1930 andredirect off surfaces S1 and S2. Example optical beam 1 is incident onS1 of the coupler structure 1930. S1 redirects the beam such that itpropagates through the waveguide 1905 via TIR towards the active area131. S2 is formed by connecting S1 to the top surface of the waveguide.Thus, beams redirected by S2 can be redirected in an undesired directionor with an undesired elevation angle. This can result in beam loss 1920.For example, optical beam 2 is incident on S2 of the coupler structure1930 and is redirected away from the active area 131. Beam loss 1920 canbe reduced by redirecting such beams back towards the active area 131e.g., by a reflector.

FIG. 20 is a perspective view of an emitter or an emitter array 2015 andcoupler structures 2030, according to an embodiment. Similar to FIG. 19,beams are emitted from an emitter array 2015, such as an array ofVCSELs. The beams travel upward and are redirected by coupler structures2030 above the top surface of a waveguide. For simplicity, the waveguideis not shown. The coupler structures 2030 can be a part of an emittercoupler. The coupler structures 2030 can be arranged such that theoptical beams propagate in a predetermined pattern. For example, thecoupler structures 2030 can be arranged such that the optical beams areevenly distributed throughout the waveguide. Furthermore, the couplerstructures 2030 can be arranged within subgroups such that apredetermined pattern includes different reflective patterns. Forexample, the one or more coupler structures 2030 can have surfaces thatredirect beams at a first elevation angle (e.g., thirty degrees) andother coupler structures 2030 can have surfaces that redirect beams at asecond elevation angle (e.g., fifteen degrees). It should be appreciatedthat an arrangement of coupler structures 2030 may be selected toachieve almost any desired distribution of beams.

Note that the emitter 2015 can be either a single emitter or an emitterarray. In the case of it is a single emitter, the population of couplerstructures 2030 can be arranged to distribute the beams in anarbitrarily complex distribution of directions, potentially with adifferent effective emitter location for each direction. If the emitter2015 is an array of emitters, then one or more of the coupler structures2030 can be associated with each element of the array and guide theemitted beams in any desired direction or directions.

What is claimed is:
 1. An optical touch-sensitive device comprising: anoptical waveguide; one or more emitters emitting optical beams thatpropagate via total internal reflection (TIR) in the waveguide, whereintouches on a surface of the waveguide disturb the optical beams, thetouch-sensitive device determining touch events based on thedisturbances; and an optical reflector on a surface of the waveguide,the optical reflector redirecting optical beams propagating in thewaveguide, wherein incident optical beams propagate through thewaveguide at an initial elevation angle and redirected optical beamspropagate through the waveguide at a modified elevation angle, theoptical reflector including reflective structures, a first one of thereflective structures comprising: a first surface oriented to redirectoptical beams incident at the initial elevation angle at the modifiedelevation angle as redirected optical beams; and a second surfaceoriented to redirect a subset of the redirected optical beams at anintermediate elevation angle towards a second one of the reflectingstructures.
 2. The optical touch-sensitive device of claim 1, whereinthe intermediate elevation angle is substantially equal to the negativeof the initial elevation angle.
 3. The optical touch-sensitive device ofclaim 1, wherein the beams propagating at the intermediate elevationangle towards the second reflecting structure are redirected by a firstsurface of the second reflecting structure at the modified elevationangle.
 4. The optical touch-sensitive device of claim 1, wherein atleast one of the reflective structures is metalized.
 5. The opticaltouch-sensitive device of claim 1, wherein the optical reflector is anintegrated portion of the waveguide.
 6. The optical touch-sensitivedevice of claim 1, wherein the optical reflector is an integratedportion of a thin film attached to a surface of the waveguide.
 7. Theoptical touch-sensitive device of claim 6, wherein a thickness of thefilm is less than or equal to 500 micrometers.
 8. The opticaltouch-sensitive device of claim 1, wherein the optical reflector heightis less than or equal to 500 micrometers.
 9. The optical touch-sensitivedevice of claim 1, wherein the modified elevation angle is substantiallyequal to the initial elevation angle.
 10. The optical touch-sensitivedevice of claim 1, wherein the modified elevation angle is smaller thanthe initial elevation angle.
 11. The optical touch-sensitive device ofclaim 10, wherein beams propagating at the modified elevation angle areless sensitive to touches than beams propagating at the initialelevation angle.
 12. The optical touch-sensitive device of claim 1,wherein the modified elevation angle is larger than the initialelevation angle.
 13. The optical touch-sensitive device of claim 12,wherein beams propagating at the modified elevation angle are moresensitive to touches than beams propagating at the initial elevationangle.
 14. The optical touch-sensitive device of claim 1, wherein thewaveguide includes at least two layers, the layers having differentindices of refraction.
 15. The optical touch-sensitive device of claim14, wherein optical beams propagating at the initial elevation anglepropagate through both layers and optical beams propagating at themodified elevation angle propagate through only one of the layers. 16.The optical touch-sensitive device of claim 14, wherein optical beamspropagating at the modified elevation angle propagate through bothlayers and optical beams propagating at the initial elevation anglepropagate through only one of the layers.
 17. The opticaltouch-sensitive device of claim 1, wherein the optical reflectorredirects some of the optical beams towards another optical reflector.18. The optical touch-sensitive device of claim 1, wherein the opticalreflector redirects some of the optical beams towards one or moredetectors or detector couplers receiving optical beams propagating inthe waveguide.
 19. The optical touch-sensitive device of claim 1,wherein the optical reflector changes a beam footprint of the opticalbeams.
 20. The optical touch-sensitive device of claim 1, wherein thereflector is placed at a periphery of a surface of the waveguide.